<p>The large spatial coverage of commercial tuna longline operations makes it crucial to compare the impact of different spatial scales on catch per unit effort (CPUE) standardization. This study utilized catch data from yellowfin tuna caught by the longline vessels in waters near Micronesia from 2019 to 2022 to compare the impact of different spatial scales (0.25° × 0.25°, 1° × 1°, and 2° × 2°) on the CPUE standardization and to explore the spatiotemporal distribution characteristics of CPUE. Spatiotemporal environmental factors and operational factors were incorporated across spatial scales using generalized additive models (GAMs). The study found that the results of CPUE standardization were significantly affected by spatial scale. The most effective model corresponded to 1° × 1° when the longline operation spanned approximately 1° in the longitudinal direction. The standardization models effectively mitigated the impact of spatiotemporal, gear-related, and environmental effects to a certain extent. The relatively high abundance index was in the first and fourth quarters, and the high standardized CPUE (value &gt; 10) was predominantly located at 4°&#xa0;N–0°. The GAM, incorporating spatiotemporal effects, has demonstrated good performance in CPUE standardization and can be an effective method when the data dimensionality is relatively low.</p>